A high-sensitivity sensor based on three-dimensional metal-insulator-metal racetrack resonator and application for hemoglobin detection

In this paper, we designed a high-sensitivity plasmonic sensor using three-dimensional plasmonic metal-insulator-metal (MIM) waveguides and a racetrack resonator. By detecting the resonance wavelength, changes in the refractive index of the resonator can be sensed, on the basis of the linear relationship between these two parameters. The structure was numerically simulated by the finite-difference time-domain method (FDTD), and the results show that the refractive index and temperature sensitivity values can be obtained as high as 4650 nm per refractive index unit (RIU) and 0.33 nm/°C, respectively. We show that such improved sensitivity can be obtained by using a long lateral interaction length along the entire flat resonator sidewalls. The effects of radius and refractive index of racetrack resonator are studied from the sensing spectra to evaluate the sensitivity performance, as well. The proposed structure with such high sensitivity will be useful in bio-sensing that can provide a new possibility for the detection of biological parameters such as hemoglobin concentration. Furthermore, the applicability of our structure in the detection of hemoglobin concentration in three different blood groups is presented.